iptables -A INPUT -p tcp --tcp-flags ALL NONE -j DROP
iptables -A INPUT -p tcp ! --syn -m state --state NEW -j DROP
iptables -A INPUT -p tcp --tcp-flags ALL ALL -j DROP
iptables -A INPUT -i lo -j ACCEPT
iptables -A INPUT -p icmp -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
iptables -I INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
apt-get install iptables-persistent